In a Long Term Evolution (LTE) system, the uplink power is controlled with the combination of an open-loop mode and a closed-loop mode. In the open-loop mode, the transmission power is adjusted by a User Equipment (UE) based on the uplink resource allocation, a transmission format, a path loss and some parameters broadcasted by a base station, while in the closed-loop mode, the uplink transmission power of the UE is adjusted by a Transmission Power Control (TPC) command sent by the base station to the UE.
The transmission power in the Physical Uplink Share Channel (PUSCH) of the UE depends on the base station, while the calculation of the transmission power is completed by the UE. The base station informs the UE about parameters necessary for the PUSCH power control at the UE through a broadcast message and Radio Resource Control signaling, and adjusts the uplink transmission power of the UE through a downlink control channel in real time; while the UE calculates the current PUSCH transmission power according to formulas prescribed in the standards and applies the power adjustment.
The transmission power PPUSCH for the UE to transmit data at an uplink sub-frame i over the PUSCH is represented by the formula below:PPUSCH(i)=min{PMAX, 10 log10(MPUSCH(i))+PO—PUSCH(j)+α·PL+ΔTF(TF(i))+f(i)}[dBm],where,    1. PMAX denotes the maximum permitted transmission power depends on the level of the UE;    2. MPUSCH(i) denotes the size of resources allocated for the PUSCH that are enabled at the ith uplink sub-frame, and is represented in the number of Resource Blocks (RBs);    3. PO—PUSCH(j) denotes an initial value of PUSCH power, and is composed of a cell dedicated normalized portion PO—NOMINAL—PUSCH(j) of 8 bits plus a UE dedicated portion PO—UE—PUSCH(j) of 4 bits. Here, PO—NOMINAL—PUSCH(j) (with j=0 and 1) is informed by a higher layer, with a dynamic range of [−126, 24] dBm and a granularity of 1 dB; while PO—UE—PUSCH(j) (with j=0 and 1) is configured by the RRC, with a dynamic range of [−8, 7] dB and a granularity of 1 dB. If the PUSCH transmission/retransmission corresponds to already configured schedule permission, j=0; and if the PUSCH transmission/retransmission corresponds to a Physical Downlink Control Channel (PDCCH) with the received Downlink Control Information (DCI) format being 0, which contains schedule permission transmitted by a new packet, then j=1;    4. αε{0, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9,1}, which is a cell dedicated parameter, denotes a compensation factor for path loss and is indicated with 3 bits by higher layer signaling;    5. PL denotes a downlink path loss measured by the UE;    6. if Ks=1.25, ΔTF(TF(i))=10log10(2MPR·Ks−1); if Ks=0, ΔTF(TF(i))=0; where Ks is a cell dedicated parameter and is indicated by RRC signaling; TF(i) denotes a PUSCH transmission format enabled at the ith sub-frame MPR=modulation×codingrate=NINFO/NRE, where NINFO denotes the number of information bits, and NRE denotes the number of resource elements determined by a transmission format TF(i) of the ith sub-frame and a resource allocation size MPUSCH(i);    7. the current PUSCH power control adjustment state is denoted by f(i), which is defined as f(i)=f(i−1)+δPUSCH(i−KPUSCH) in the case of an accumulated adjustment mode, and f(i)=δPUSCH(i−KPUSCH) in the case of an absolute adjustment mode;where, in the case of f(i)=f(i−1)+δPUSCH(i−KPUSCH), then
(1) f(0)=0, KPUSCH=4;
(2) δPUSCH denotes an accumulated correction value and is obtained through decoding from a TPC command received at the (i−KPUSCH)th sub-frame which is ahead of the ith sub-frame by a number KPUSCH of sub-frames, for example, if i=10, δPUSCH is obtained through decoding from the TPC command received at the 6th sub-frame;
(3) when the TPC command cannot be obtained through decoding or the UE is in a DRX state, a δPUSCH=0 dB;
(4) the accumulated correction value δPUSCH may be of a value selected from a set of [−1, 0, 1, 3] when it is indicated by PUSCH having a DCI format of 0;
(5) the accumulated correction value δPUSCH may be of a value selected from a set of [−1, 1] or [−1, 0, 1, 3] when it is indicated by PUSCH having a DCI format of 3/3A, and whether [−1, 1] or [−1, 0, 1, 3] is selected is semi-statically configured at the higher layer;
(6) if the maximum transmission power of the UE is reached, any “positive” TPC command is not accumulated;
(7) if the minimum transmission power of the UE is reached, any “negative” TPC command is not accumulated; and
(8) the accumulation of TPC commands needs reconfiguration for the UE in any of states selected from a) when a cell of the UE is updated, b) when the UE enters/quits an RRC activated state, c) when a TPC command in the absolute adjustment mode is received, d) when PO—UE—PUSCH(j) notified by the RRC is received, and e) when the UE is in a synchronizing/re-synchronizing state;
where in the case of f(i)=δPUSCH(i−KPUSCH), then
(1) δPUSCH denotes an absolute correction value and is obtained through decoding from a TPC command received at the (i−KPUSCH)th sub-frame which is ahead of the ith sub-frame by a number KPUSCH of sub-frames;
(2) KPUSCH=4;
(3) the absolute correction value δPUSCH may be of a value selected from a set of [−4, −1, 1, 4] when it is indicated by PDCCH having a DCI format of 0; and
(4) when the TPC command cannot be obtained through decoding or the UE is in a DRX state, f(i)=f(i−1).
The UE selects the accumulated adjustment mode or the absolute adjustment mode according to the RRC instruction.
The KPUSCH is a delay of TPC controlling for PUSCH, and the TPC used for transmitting uplink data at the ith sub-frame is actually transmitted via control signaling at the (i−KPUSCH) sub-frame by the base station. Typically, in a Frequency Division Duplex (FDD) system, the delay caused by the processing of the downlink control signaling by the UE is no more than 3 ms, and thus KPUSCH=4.
In a TDD system, however, the delay of TPC controlling cannot be set as a predefined value due to the presence of a plurality of uplink and downlink sub-frame allocation modes (as shown in FIG. 1) and the case of multiple frame schedule where a plurality of uplink sub-frames are scheduled by each schedule signaling command; in addition, there is no available method for determining the delay of TPC controlling in the TDD system at present, and the mapping between an uplink sub-frame and the downlink sub-frame transmitting the TPC command cannot be established, such that the UE cannot determine the downlink sub-frame from which the TPC command can be obtained when the UE attempts to control the power used for transmitting data via a certain uplink sub-frame, and thus cannot determine the transmission power according to the parameter δPUSCH in the TPC command. That is, the uplink power control cannot be achieved properly and effectively in the TDD system.
FIG. 1 shows seven uplink and downlink sub-frame allocation modes 0-6 in the existing TDD system.
The uplink and downlink sub-frame allocation modes 0-2 each have a switch point periodicity of 5 ms. In the mode 0, each half-frame is composed of 1 downlink sub-frame (D), 1 special sub-frame (S) and 3 uplink sub-frames (U); in the mode 1, each half-frame is composed of 2 downlink sub-frames, 1 special sub-frame and 2 uplink sub-frames; and in the mode 2, each half-frame is composed of 3 downlink sub-frames, 1 special sub-frame and 1 uplink sub-frame.
The uplink and downlink sub-frame allocation modes 3-6 each have a switch point periodicity of 10 ms. In the mode 3, each half-frame is composed of 6 downlink sub-frames (D), 1 special sub-frame (S) and 3 uplink sub-frames (U); in the mode 4, each half-frame is composed of 7 downlink sub-frames, 1 special sub-frame and 2 uplink sub-frames; in the mode 5, each half-frame is composed of 8 downlink sub-frames, 1 special sub-frame and 1 uplink sub-frame; and in the mode 6, each half-frame is composed of 3 downlink sub-frames, 2 special sub-frames and 5 uplink sub-frames.
The special sub-frame includes a downlink special timeslot (i.e. Downlink Pilot Timeslot, DwPTS), a switch point timeslot (i.e. Guard Period) and an uplink special timeslot.